Liquid-dispensing device

ABSTRACT

In studying surfaces a volatile material is applied to the surface and its rate of evaporation therefrom is followed, the values obtained being compared to the rate of evaporation from control surfaces. By this approach one can study the amount of contamination on the surface being tested, the nature of the said surface and similar factors. Apparatus and compositions of matter for effecting such studies are described and claimed in Ser. No. 506,566, now U.S. Pat. No. 3,412,247. The present application and invention relates to certain pieces of apparatus used in such studies. Particularly, this invention relates to apparatus for dispensing the volatile materials that are applied in conjunction with a detection device used in following the rate of evaporation of the volatile materials. The dispenser is a device which contains a reservoir for the volatile material positioned in the device so that it can be placed in conduit relationship with an outlet for the said materials allowing for the placement for those materials on the surface to be tested. Contained in the dispenser are a charge pump and a discharge pump which can be placed in conduit relationship with said reservoir and with said outlet as desired to effect the removal of a metered amount of the volatile materials as desired. The detecting device comprises a means for following the rate of evaporation of the volatile materials and a means for passing a controlled flow of gas between the detecting device and the surface containing the volatile materials. Generally, the volatile materials contain a radioactive material and the means for detecting is a means for detecting radiation such as a Geiger-Mueller counter. The detecting device also generally contains a means for controlling the flow of gas, a means for filtering the gas to eliminate contaminants and a means for placing the detecting device into a desired position in relationship to the surface being tested.

United States Patent [72] Inventor John LyndeAnderson 542 Union Avenue,New Providence, NJ. 07974 [21] Appl No. 776,745 [22] Filed Nov. 18, 1968Division of Ser. No. 506,566, Nov. 5, 1965,

Pat. No. 3.412.247. which is a continuationin-part of application Ser.No. 161.246. Dec. 21. 1961, now Patent No. 3.297.874. [45] Patented June1,1971

[54] LIQUID-DISPENSING DEVICE 9 Claims, 24 Drawing Figs. [52] US. Cl250/106, 222/251, 222/332, 250/43.5 [51] int. C1 G0lt 7/02 [50] Field ofSearch 250/43.5 R, 106 T; 222/251, 264, 332, 424.5, 425

[56] References Cited UNITED STATES PATENTS 1,815,875 7/1931 Muller222/425X 1,879,109 9/1932 Coy 222/332 2,385,378 9/1945 Piety 250/83.6W2,869,761 l/1959 Meyer et a1... 222/425 3,290,501 12/1966 Schiff250/106SC 3,315,077 4/1967 Jones, Jr. et a1. 250/106SC PrimaryExaminer-Archie R. Borchelt Attorney-C. Walter Mortenson ABSTRACT: Instudying surfaces a volatile material is applied to the surface and itsrate of evaporation therefrom is followed, the values obtained beingcompared to the rate of evaporation from control surfaces. By thisapproach one can study the amount of contamination on the surface beingtested, the nature of the said surface and similar factors. Apparatusand compositions of matter for effecting such studies are described andclaimed in Ser. No. 506,566, now U.S. Pat. No. 3,412,247. The presentapplication and invention relates to certain pieces of apparatus used insuch studies. Particularly, this invention relates to apparatus fordispensing the volatile materials that are applied in conjunction with adetection device used in following the rate of evaporation of thevolatile materials. The dispenser is a device which contains a reservoirfor the volatile material positioned in the device so that it can beplaced in conduit relationship with an outlet for the said materialsallowing for the placement for those materials on the surface to betested. Contained in the dispenser are a charge pump and a dischargepump which can be placed in conduit relationship with said reservoir andwith said outlet as desired to effect the removal of a metered amount ofthe volatile materials as desired. The detecting device comprises ameans for following the rate of evaporation of the volatile materialsand a means for passing a controlled flow of gas between the detectingdevice and the surface containing the volatile materials. Generally, thevolatile materials contain a radioactive material and the means fordetecting is a means for detecting radiation such as a Geiger-Muellercounter. The detecting device also generally contains a means forcontrolling the flow of gas, a means for filtering the gas to eliminatecontaminants and a means for placing the detecting device into a desiredposition in relationship to the surface being tested.

CLiNOME ER PATENTEU'JUN 1 Ian 3,582,657

sum 1 a? 6 IN VENTOB v y J lglgizdgflnderson ATTORNEY ATENTED JUN 119m3:582 657 sum 2 or 6 INVENTOR J ohn L ynda fllzdersozz j 55 I I 61 EWflL-Am ATTORNEY PATENTED 11111 1 1911 3.582.657 SHEET 5 OF 6 .16. 17gBackgroundReadug P016161 1? P61610151 L0101 1 1 L01010141 AA A8 A0 A1)Fig. 16A. Tesi of Validig (c lean) [01018127 lOlOll [e7 Lo|o|o171lolololafi 1 AA B A0 AD 17H. 1 Readily offiryezprint smudge 101113101 Q11011? 101018101 13 17-10 0 0 0 \.A A15 A0 A1) 1 27.166. Readiqqafierfvysrprini is 1114060? ofi |0l1|1|5l lololaa] m 9 [MOO8 AA AB Ac 1Al) F .15. 0 M 72 l i HV: 1 27p p b 115 A zg GMDeZecio: 215 g g ConirolN2] (43 j l Macroswdch \10 99 31 F 7 70a INVENTOR John Lynda flrzdersonATTORNEY PATENTEHJUN HSYI 3,582.85?

sum 6 or 6 v IN VENTOB' J 1112 L a? By 0 A11 501:

ATTORNEY LllQUllD-DHSIPENSTNG DEVlIClE This case is a division of myapplication Ser. No. 506,566, filed Nov. 5, 1965, now U.S. Pat. No.3,412,247, which case was a continuation-in-part of my application Ser.No. 161,246, filed Dec. 21, l96l,now U.S. Pat. No. 3,297,874.

DlSPENSER AND PROCESS This invention relates to a new method ofdetecting contamination on surfaces and more particularly to thedetection of nonvolatile organic contamination on metal and othersurfaces.

The rapid and quantitative detection of nonvolatile organic contaminantseither on metal or other surfaces or within spaces confined by suchsurfaces, particularly contaminants which are present only in very smallamounts, is not practicable using existing methods and techniques. Thus,a method in general use involves the process of thoroughly wetting ametal surface with a solvent for the contaminant, of recovering thesolvent quantitatively and then determining the amount of contaminantdissolved in the solvent. This method, however, determines only materialwhich is removed from the surface and does not determine material whichis left on, or is adjacent to, the surface after the test is completed.While it is known that the cleanliness of a surface can be determined byuse of radioactive materials, the prior art methods, as, for example,that of Dvorltovitz et al. described in U.S. Pat. No. 2,968,733, are notadequate and not always operative, for the problem of contamination ofmetal surfaces often is a most serious one, particularly when thecontamination may cause explosions or rapid, uncontrolled chemicalreactions when in contact with other material for which the surface inits various forms is designed. For example, in handling liquid oxygen itis essential that the amount of organic contamination on the metalsurfaces over which the liquid oxygen is standing or through which it istransferred must be kept to the irreducible minimum and must bequantitatively determined prior to permitting the liquid oxygen to comeinto contact with metal surfaces involved, in order to insure maximumstability and safety. Testing procedures which introduce or leavecontaminants behind must be avoided.

it is, therefore, an object of this invention to provide a new anduseful method for the detection of contamination on surfaces. Anotherobject is the provision of a method for the detection of nonvolatileorganic contamination on metal surfaces or within spaces confined bymetal surfaces by a simple and economical method. A still further objectis the provision of a method by which nonvolatile hydrocarboncontamination on metal surfaces may be detected. Other objects willappear as the description ofthe invention proceeds.

These and other objects are accomplished in the present invention byapplying a volatile radioactive labeled compound to a surface, bypartially evaporating the radioactive labeled compound and at the sametime evaporating substantially all of the solvent, if any, used to applythe labeled material, and by detecting the amount of radioactivity whichis left on the surface being examined, the amount of remainingradioactivity after such evaporation retained on a previouslyscrupulously clean surface similarly treated being always less than thatwhich is left on a contaminated similar surface and therefore the ratioof the amount of radioactivity on the con taminated surface to theamount on the previously scrupulously clean surface being a directmeasure of the amount of contamination.

Another embodiment of my invention is accomplished by applying avolatile radioactive compound into the space enclosed by a surface, bypartially evaporating the radioactive compound and at the same timesubstantially all of the solvent, if any, used to apply the labeledmaterial, and by detecting the amount of radioactivity which is leftretained within the space enclosed by the surface, the amount ofradioactivity remainingafter such evaporation from within the previouslyscrupulously cleaned space enclosed by a surface being less than thatwhich is left within a contaminated space enclosed by a surface andtherefore the ratio of the amount of radioactivity within thecontaminated space enclosed by the surface to the amount within thepreviously scrupulously cleaned space enclosed by the surface being ameasure of the amount ofcontamination.

More particularly my invention includes the process of applying avolatile radioactive labeled compound, preferably chemically compatiblewith the organic materials which are normally found on metal or similarsurfaces or within spaces confined by such surfaces, to such a surfaceor to within spaces confined by such surfaces, of partially evaporatingthe radioactive compound after such application only to the extent thatthe radioactive compound would substantially completely evaporate from apreviously scrupulously clean surface or from within previouslyscrupulously clean spaces enclosed by a surface, of determining theresidual radioactivity, and thus of detecting the contaminant.

A preferred embodiment of my invention is achieved by applying avolatile radioactive labeled compound to the surface, by partiallyevaporating the radioactive labeled compound and at the same timeevaporating substantially all of the solvent, if any, used to apply thelabeled material, and by detecting the amount of radioactivity which isleft on the surface being examined and therefore a measure of the amountof contamination.

This invention will be further understood by reference to thedescription and to the examples given below which are given for purposesof illustration only and are not to be taken as limitative. in theexamples, any parts of percentages given are by weight unless otherwisespecified.

EXAMPLE] Ten parts of a solution of 2,000. parts of trichloroethyleneand 1 part of l-decylbromide-l-C" containing a total of 20 microcuriesof radioactivity is added to a stainless steel surface containingdispersed uniformly on the surface 20 micrograms of nonvolatilehydrocarbon per square inch of surface area. A similar amount of theradiochemical solution is added to a scrupulously clean stainless steelsurface of similar area. Evaporation of each solution-wetted area iscarried out for a period of 45 seconds with a slow stream of dry gaseousnitrogen. Detection of the residual radioactivity on each surfacedemonstrates that the originally contaminated surface exhibits twice theactivity of that shown by the originally scrupu= lously clean surface.

EXAMPLE 11 One thousand parts of tetrachloroethylene-C containing 50microcuries of radioactivity dispersed as liquid droplets in dry gaseousnitrogen is passed slowly through a 6 inch diameter scrupulously cleanstainless steel tube containing a small amount of paper saturated with anonvolatile hydrocarbon wax. Following flushing of the entire stainlesssteel pipe with sufficient dry gaseous nitrogen to reduce the activityon the previously scrupulously clean surface so as to be virtuallynondetectable over the background radiation, the paper saturated withhydrocarbon wax exhibits a significant and higher radioactivity levelthan does the adjacent metal surface.

EXAMPLE III Three parts (0.1 milliliter) of a solution consisting of 8milli-- grams of decyl bromide-LC of specific activity 0.62 mc/mM(millicuries per millimole) in 25 milliliters of methylene chloride isadded to the surface of a scrupulously clean glass plate and the rate ofevaporation measured by recording the disappearance of radioactivityfrom the surface. As the solvent methylene chloride evaporates thecounts per minute in creases to a maximum and then rather sharply fallsoff and rapidly approaches the normal background when the radioactivityis measured by means of a thin window Geiger counter positionedapproximately one-half inch above the surface of the glass. Theevaporation is controlled in part in this experiment by flowing over thesurface of the glass plate a steady stream of clean dry nitrogen gas.The radioactivity as measured by the Geiger counter is recorded incounts per minute on a strip chart recorder. In this experimentbackground levels of radiation are reached in approximately 70 seconds.When an artificially contaminated similar glass plate to which Imicrograms of crankcase grease has been added is treated similarly andthe rate of evaporation observed under identical conditions oftemperature and nitrogen gas flow, the rate of evaporation markedlydecreases and in 70 seconds the radiation levels have decreased from ahigh of 700 counts per minute to approximately 200 counts per minute.

When a glass plate is contaminated with 250 milligrams of crankcasegrease and all other conditions are held constant, the radiation levelsdecrease by only approximately 50 percent over the same time period.

Similarly through not identical results are obtained when the surfaceunder test is aluminum, polypropylene, nylon, and stainless steel.

EXAMPLE lV When the surface being examined in Example III is an interiorsurface of a steel tank and the rate of nitrogen gas flow is markedlyincreased, the evaporation from a scrupulously clean surface is nowsubstantially complete in 35 seconds and evaporation from a contaminatedsurface (100 milligrams of grease) is not substantially complete after60 seconds.

EXAMPLEV One hundred lambda (0.1 milliliter) of a low boiling petroleumether solution containing 2 microcuries of nonanoll-C (specific activityof 2.0 mc/mM per milliliter of solution) is added to a scrupulouslyclean glass plate and a stream of clean dry nitrogen gas is thendirected onto the surface. The radioactivity in counts per minutemeasured onehalf inch above the surface by a Geiger-Mueller thin windowtube ratemeter is recorded on a strip chart. Following evaporation ofthe solvent the residual nonanol-l-C" evaporated substantially tobackground (less than 50 counts per minute) within 30 seconds from ahigh of 1,000 counts per minute.

When this experiment is repeated using a glass plate on which has beendeposited 80 micrograms of crankcase grease the evaporative curve (asmeasured by the disappearance of radioactivity) shows a maximum of 1,200counts per minute and a reduction to 250 counts per minute after 50seconds.

The slope of the evaporative curve obtained by expressing counts perminute against time in seconds at l0 seconds from maximum isapproximately 40 for the scrupulously clean surface and only for thecontaminated surface.

Substitution of an aluminum surface for the glass plate does notmaterially affect the rate of evaporation under either condition.

EXAMPLE Vl In an experiment similar to Example V, the contaminationintroduced is 4 milligrams of shredded filter paper. Under similarconditions of temperature and gas flow, the evaporation rate isintermediate and decreases from a maximum of 1,250 counts per minute to200 counts per minute in 70 seconds.

EXAMPLE Vll Dry air at 50 C. is led slowly from the bottom up through avertical glass tube two meters in length which tube contains atetrachloroethylene solution in which has been dissolved 3 millicuriesof l,l ,2,Z'tetrabromOethane-Br (specific activity of 3.0 mc/mM) andheld at 50 C. The resultant saturated gas containing as vapor bothtetrachloroethylene and l,l ,2,2- tetrabromoethane-Br" is then led intoa scrupulously clean 3 inch stainless steel pipe and valve assembly alsoheld at 50 C.

and into which has been introduced mg. of machine oil at one flangeposition joining the pipe and a valve. Following detection ofradioactivity in substantially the same concentration per unit volume ofeffluent gas as is observed in the inlet gas the flow is stopped and thepipe and valve assembly isolated. The assembly is then permitted to coolto ambient temperature, that is to about 30 C. Measured externally witha scintillation counter, radiation is detected along the length of thepipe and valve assembly and a somewhat greater amount of radiation isdetected adjacent to the contamination. Dry purge air is then meteredslowly into the pipe and valve assembly and the rate of evaporation ofthe condensed l,1,2,2- tetrabromoethane-Br" into the purge gas ismeasured all along the pipe and valve assembly as the front of the purgegas progresses along the length. The rate of evaporation into the purgegas is observed to be similar throughout the pipe and valve assemblyexcept in the area of the machine oil contamination where the rate issignificantly lower.

Somewhat similar results are obtained when the evaporation is caused byevacuating the pipe and valve assembly and causing the condensed liquidsto vaporize.

When these experimental conditions are observed in similar assemblies ofglass, monel, aluminum, and linear polyethylene, similar evaporativeresults are obtained. Small effects are sometimes observed for changingsurface conditions and surface materials in that the rate ofevaporationfrom the clean surfaces vary slightly but in each case the rate ofevaporation is considerably lowered in the adjacency to thecontamination.

When the experimental conditions are repeated except that thecontaminant is (1) code liver oil and (2) ivory soap, similar resultsare obtained.

EXAMPLE Vlll In an experiment similar to Example VII the location of thecontaminant is likewise confirmed when the solvent is butanol and theradioactive material iodoacetic acid-l and the contaminant 500milligrams of proteinaceous residue.

EXAMPLE lX In an experiment similar in radioactive material, solvent,temperature, surface, and nitrogen purge gas as in Example V, thepresence of 10 milligrams of carbon black on a machined nylon surface isreadily demonstrated in that the rate of evaporation is very much slowerthan from a clean nylon surface.

EXAMPLE X An aerosol package contains perfluorocyclobutane aspropellant, 10.0 milliliters of methylene chloride and 50 microcuries ofl ,l ,2,2-tetrabromoethane-C (specific activity 3.5 mc/mM). Whenapproximately one-tenth microcurie per sq. in. is sprayed onto a cleanmachined brass surface of 10 square inch area and the solvent isevaporated under a steady stream ofair at 30 C., the residuall,l,2,2-tetrabromoethane- C" disappears at a rate which indicatesvirtually complete evaporation in a period of 100 seconds, the radiationbeing detected with a thin window Geiger counter mounted one-half inchfrom the brass surface.

When the brass surface is contaminated with cutting oil at a level of 10milligrams per square inch and the aerosol application repeated and dryair is blown over the surface at the same rate, the rate ofevaporationis slowed markedly and easily detectable residues of l, l,2,2-tetrabromoethane-C are observed even after 250 seconds.

EXAMPLE Xl Results somewhat similar to those obtained in Example X areobserved where the aerosol package contains only perfluorocyclobutaneand l,l ,2,2-tetrabromoethane-C"; that is, the methylene chloride iseliminated, showing that additional solvents are not essential.

EXAMPLE xn Fifty parts of a solution containing 0.l microcuries ofcarbon I4 labeled tetrabromoethane (specific activity 85 millicuries permillimole) dissolved in 150,000 parts of trifiuorotrichloroethane,removed from a sealed ampule of 3 mm. outside diameter and drawn to astandard capillary on each end, was added to a l inch length of a 55denier acetate rayon yarn containing a standard finish which length waspositioned on a stainless steel surface. The addition was such that thefiber surfaces were substantially wetted by the liquid. Immediatelyafter the application of the radiochemical solution, a thin end windowGeiger-Mueller detector, protected with a 0.15 mil Mylar shield, waspositioned directly above the wet fibers and a constant flow of cleandry nitrogen passed over the sample and below the surface of the tubeprotection shield. Following evaporation of the solvent, the rate ofevaporation of the radioactive labeled material was observed by plottingthe counts per minute versus time and the areas under the evaporationcurve measured by taking the total digital information obtained from theGeiger tube, analyzing the data and expressing on a timed basis foursequential areas under the evaporation curve, as explained below. Theseareas provided the following numbers: 68, 57,50, 46.

A similar determination made on identical fibers in the absence offinish provided similar number values of l5, l2, 9, 7. The highernumbers are a measure of the amount of finish.

When varying amounts of finish are applied to similar rayon fibers, thenumbers obtained were always in a ratio relative to the amount of finishapplied. Thus, this procedure can be used as an accurate measure of theamount of finish on fibers.

In a similar experiment the volatile solvent used was cyclopentane andthe radiochemical was tridecane-C" with a specific activity of at least40 millicuries per millimole. Similar, but not identical numericalresults were obtained.

In another similar experiment, the radiochemical test solution usedconsisted essentially of the dimethyl ether of triethylene glycol Cdissolved in the volatile solvent diethyl ether. Similar but notidentical results were again obtained. These experiments show that theamount of surface residue on the rayon fibers may be detected by thistechnique with different radiochemicals.

EXAMPLE XIII Using the precision volumetric dispenser described hereinin FIG. 1, among others, a lambda volume of radiochemical test solutioncontaining 1 part of tetrabromoethane-C dissolved in 60,000 parts oftrifiuorotrichloroethane was added dropwise to a flat, horizontal andclean silicon surface. Following the positioning of a suitable detectorabove and impingement of dry gas nitrogen onto the surface, thedesorption rate from the surface was observed. Expressing the areasunder the evaporation curve as a direct function of the digitalinformation, and permitting the prior evaporation of solvent, onlybackground radiation could be detected in four sequential periods. Whenthe same surface was contaminated with 20 micrograms of oil andsimilarly examined, the numerical expressions were 35,28, 24 and 22,thus detecting and measur ing the contamination.

EXAMPLE XIV In an experiment similar to Example XII, l inch of nylonmonofilament having a standard processing finish on its surface was cutinto one-eighth inch lengths and the eight pieces were positioned on asample plate of glass which contained a standard concavity 5 mm. indepth and 25 mm. in diameter for each filament. Then 0.5 ml. of ethylether was added to the fiber located in the concavity and the shortlengths of fiber were removed with a scrupulously clean pair offorcepts. Following evaporation of the ethyl ether, 50 lambda of asolution containing 0.5 micrograms of tetrabromoethaneC in methylenechloride was added dropwise to the residue. Following evaporation of thesolvent methylene chloride, the

evaporation rate of the radioactive material was determined by passing acontrolled flow of pure nitrogen gas at a rate of l,200 ml. per minuteover the surface and between the surface and a thin end window G. M.tube. The various discharges in the G. M. tube were analyzed by theequipment shown herein and the counts per minute plotted against time ona strip chart recorder. The rate of evaporation of the radioactivematerial thus obtained was significantly lower than the rate observedwhen the same experiment was carried out on nylon monofilament which hadbeen previously scrupulously cleaned of finish.

EXAMPLE XV One cubic centimeter of ether containing l0 parts per millionof nonvolatile residue was evaporated into a glass planchet similar tothat used in Example XIV, and the nonvolatile residue on the planchetwas permitted to resume ambient temperature. Then 8 lambda of a solutioncontaining tetrabromoethane-C dissolved in trifluorotrichloroethane wasadded to the planchet and the volatile solvent evaporated. Subsequentmeasurement of the rate of evaporation of the radioactivetetrabromoethane-C from the surface showed the presence of thenonvolatile residue previously deposited from the ethyl ether. When theidentical experiment was carried out using ethyl ether of scrupulouspurity, the observed rate of evaporation was much faster and in factunder the conditions of the experiment, background levels were reachedin a few seconds whereas background levels were reached only afterseveral minutes in the ease of the deposited residue.

EXAMPLE XVI In an experiment similar to Example XV, the amount ofnonvolatile residue in a series of samples of trichloroethylene whichhad been obtained from washing the internal surfaces of piping used inpumping hydraulic oils showed that the rate of evaporation increasedwith the residues laid down from samples taken sequentially. This showedthat the first samples contained higher amounts of residual oil andlater samples lower amounts. By using this technique the efficiency ofthe cleaning steps and materials can be rapidly determined.

EXAMPLE XVII Fifty parts of a solution containing tridecane-C" ofspecific activity 40 millicuries per millimole in 100,000 parts byweight of pentane is added to the surface of a tin plate to which hadbeen added by spraying 1.15 grams of oil per 62,000 square inches ofsurface. Following evaporation of the pentane the rate of desorption ofthe radioactivematerial from the surface and from the contaminant wasobserved by use of a thin end window G. M. tube and counting systemusing a steady stream of filtered air as the evaporation agent. The rateof desorption or evaporation from the contaminated surface wassignificantly lower than when the similar procedure was carried out onpreviously cleaned tin plate. When the same type of test was run onseveral different spots on the same piece of tin plate, variousdecreased rates of evaporation were observed showing that the sprayingtechnique employed for laying down the oil film did not provide uniformcoverage of the surface. Several oils were tested including dioctylsebacate and cottonseed oil.

In a similar experiment, a solution of tetrabromoethane-C" intrifluorotrichloroethane in 1260,000 ratio by weight was used to provethe presence of 6 milligrams per square foot of stearic acid on aluminumfoil. The evaporation rate was always significantly lowered by thepresence of contaminant and the results of several spot tests showed adecided unevenness in amount of stearic acid on the surface.

EXAMPLE XVIII Fifty lambda of a solution containing 0.5 micrograms oftetrabromoethane-C in trichlorotrifiuoroethane and substantially nononvolatile residue was added, from a previously sealed 2 mm. (outsidediameter) glass tubing, in which the solution formed a steady miniscuswhen inverted by breaking off first one end of the tube and then asecond end, to a concavity in a stainless steel planchet on which hadbeen deposited previously micrograms oflinseed oil followed by curing inan air oven for minutes at 100 C. The results of observing the rate ofevaporation using the equipment described herein showed values of I10,92, 84, and 76 whereas the same determination in the absence of thelinseed oil showed values of 60, l5, 7 and 4, respectively. When thetest plate was cleaned in an ultrasonic cleaner for a period of 8minutes using trifluorotrichloroethane as solvent, a sub sequent testshowed that substantially all ofthe linseed oil had been removed whenthe values of56, l4, 8 and 5, respectively, were obtained. These valueswere obtained using the apparatus of this invention described below.

When the same test was performed with another ultrasonic cleaner, theresults following the 8 minute cycle showed values of 70, 24, 13, and 8showing that the second ultrasonic cleaner did not function as well asthe first one.

When the same test was performed with yet another ultrasonic cleaner,the results showed that this third cleaner barely cleaned the surface atall; that is, the results following cleaning were 90, 78, 69, and 62.

Thus, the method of observing comparative rates of evaporation onpreviously similarly contaminated surfaces permits an accurate andinstrumental evaluation of the efficacy ofultrasonic cleaners.

In still another experiment a mixture of decyl bromide-l- Br andnonanol-l-C is used as the radioactive element in order to effectpreferential pickup by contaminants varying in chemical composition. Itis noted that this combination works well with contamination containingboth carbohydrates and hydrocarbonaceous materials. Similarly, othermixtures of contaminants are treated with radioactive materialspurposely compounded in mixtures to insure good pickup by eachindividual contaminant in the composite impurity.

From the above it can be seen that in my invention a volatileradioactive labeled compound is used which preferably is compatible andmiscible with the type of contaminant which it is desired to detect andto measure, and in general it is preferred that the radioactive labeledcompound is chemically inert with both the surface and with thecontaminant. In the event that the radioactive labeled compound selectedis, in fact, reactive with the contaminant, it is necessary that thecompound will be much less reactive with the surface itself so thatafter the evaporative phase of my invention, a difference inradioactivity will be observed. In addition, the labeled compoundselected for a given surface or combination of surfaces will have avolatility which is normally less than the volatility of the particularsolvent employed, if any. In any event the volatility of the radioactivelabeled compound is such as to permit substantially complete evaporativeconditions even when the surface is contaminated. Under these conditionsthe detection of residual radioactivity on the surface constitutes apositive demonstration that the contamination existed prior to theapplication of the test solution of the radiochemical.

The amount of radioactivity which is detectable is in generalproportional to the amount of contamination which was originally presentwhen the process of my invention is employed. The physical state and thechemical nature ofthe contamination also affect to some degree theamount of residual activity detected and the amount of radioactivelabeled compound retained under the evaporative conditions. A smallamount of contamination will cause the retention of only a small amountof residual activity whcreas a large amount of chemically similarcontamination will cause the retention ofa relatively large amount ofresidual activity. The rate at which the solvent, if any, and theradioactive labeled compound are evaporated is not highly significant;however, the evaporative conditions are normally continued untilsubstantially all ofthe solvent and the radioactive material wouldevaporate if no contaminant on the surface were originally present; thatis, control conditions are met.

The type of contamination which is detected by my inventive process isthat which is often found on metal surfaces. Such contamination mayarise from cutting or threading oils, from greases and protectivehydrocarbons, and in other ways. The particular radioactive labeledcompound employed will determine in part the efficacy of the detectionprocess and it is preferred that radioactive compounds be used which arecompatible with hydrocarbons and other organic contaminants.

The particular radioactive labeled material employed in my invention isselected also for the type and energy of radiation emitted, for thechemical compatibility which the solvent used, if any, for the abilityto be absorbed on the surface of or absorbed within the contaminant andfor such volatility as to enable substantially complete evaporationwithin a reasonable time from a previously scrupulously clean surface.The radioactive labeled compound is made radioactive by the presence ofalpha, beta, or gamma emitting radioisotopes. In general for measuringthe radioactivity immediately adjacent to the contamination, compoundscontaining soft beta or gamma emitters are used while compoundscontaining hard beta or gamma emitters are required when theradioactivity is detected through a metal surface.

A preferred class of radioactive labeled compounds consists of organiccompounds which are labeled with at least one of the group of betaemitters consisting of carbon-l4, sulfur-35, phosphorous-32, chlorine-36and hydrogen-3. Another preferred class of radioactive labeled compoundsconsists of organic derivatives containing one or more strong gammaemitter.

Some typical classes of volatile radioactive labeled compounds which arewell suited for my invention are the hydrocarbons decane-C",tridecane-C", decalin-C", isooctane-C, and nonane-H; halohydrocarbonssuch as decyl bromide-C, tetrachloroethylene-C", trichloroethylene-C',hexachloropropene-C, carbon tetrachloride-C", chloroform- C, anddifluorotetrachloroethane-C ethers and thioethers such as ethyleneglycol diethylether-C", and dibutylthioether- S; and phosphorouscompounds such as tripropylphosphine and phosphorous tribromide labeledwith phosphorous-32.

The radioactivity in my inventive process is detected by means of anysuitable detector of radiation. For most purposes a Geiger-Mueller tubeand associated equipment is acceptable and convenient. Portableinstruments used to detect radioactivity inside of long and complexmetal tubes have had to be designed for this purpose.

The surfaces examined by my inventive process may be almost any materialused in commerce for construction of plates, pipes, valves, tanks,flanges, and the like. For example, metal, glass, fused ceramics, andplastic surfaces are all satisfactory and may be examined for thepresence of contaminants. In general, the more porous the surface (thatis, the greater the surface area) the less the differentiation betweensurface and contaminant with respect to retention of radioactive labeledmaterial and therefore the less positive the absolute identification ofcontaminant. To illustrate, oil or grease is very readily detected onpolished stainless steel but oil or grease on a surface prepared bycompressing finely divided carbon black is more difficult to detectsince the carbon black with a relatively high surface area absorbs theradioactive labeled material in much the same way as the contaminantabsorbs it and the rate of evaporation from the compressed carbon blackis nowhere near as rapid as from polished metal or glass. But by properreference to the control the presence of the contaminant is detected aswell as a fairly quantitative measurement of it. Knowing the nature ofthe surface, the operator ofthis invention will proceed accordinglyv Itis apparent from this discussion that materials such as sand or finelydivided iron oxide may be readily detected on the surface of machinedsteel using my invention provided a radioactive labeled material isselected which is absorbed more strongly by contaminants, such as ironoxide, than by the machined surface, since the evaporative rate from theiron oxide is less than that from the machined steel, other conditionssuch as temperature and flow of gas over the surface being heldconstant.

Solvents such as tetrachloroethylene in Example VII and low boilingpetroleum ether in Example V are not an essential part of this inventionin its broadest aspects although in preferred embodiments solvents areused. Solvent functions are to increase the solubility, the rate ofsolution, and/or the adsorption or absorption of the radioactive labeledcompounds on or in the contaminant to be detected. In addition thepresence of the solvent tends to increase the efficieney of thedeposition on all surfaces, as is shown in Example Vll. Many solventsmay be used such as tetrachloroethylene, low boiling petroleum ether,butanol, perfluorocyclobutane, methylene chloride, ethanol, acetone,formic acid, ethyl ether, and the like. Solvents with boiling points atleast 100 C. less than the boiling points of the particular radioactivelabeled material are used in order that appreciable residues of theradioactive labeled material are left over after substantially completeevaporation of the solvent.

In general, it is preferred to use a radioactive labeled material whichhas a boiling point at least 100 C. higher than the solvent boilingpoint in order to insure that, following the evaporation of the solvent,sufficient radioactive labeled material is left behind for readydetection particularly in the case of previously scrupulously cleanedsurfaces. Therefore, materials with boiling points in excess of 100 C.are preferred when low boiling solvents are employed and in excess ofl30 C. when higher boiling solvents are employed. When no solvents areemployed in my inventive process, the boiling point of the selectedradioactive labeled material should be sufficiently high so that faciledetermination of the rate of evaporation is possible.

When two or more types of contaminants may be encountered, it is ofadvantage to use two or more particular radioactive labeled materials ofsuch a nature that one is absorbed more strongly by a first type ofcontaminant and so forth. Thus, when attempting to locate and detectcontaminants such as hydrocarbon grease and proteinaceous material,radioactive labeled materials such as l,l,2,2,- 'tetrabromoethane-Br andiodoacetic acid-l may be used simultaneously in the same solvent ordispersant system. Also, the rate of evaporation of each may bedetermined independently of the other by means of suitable detectiondevices such as scintillation or solid-state detectors coupled withchannel analyzers so that the individual radiations of different energylevels are determined separately. This technique permits the detectionof the location, the type, and the relative amount of each contaminantquickly and conveniently. Other counters which can be used include theGeiger counter and the proportional counter for beta and gamma rays.These various counters may be used externally or as probes moving withinthe enclosures being tested.

When using my inventive process, and particularly the aerosol method,many different types of propellants and/or solvents may be used. Thus,octafluorocyclobutane, dibromodifluoromethane, nitrogen, nitrous oxide,butane, and the like may be used. Normally, it is desired to usenonflammable materials, such as the polyhalogenated materials. Includedamong these are monofluorotrichloromethane, chloroform, carbontetrachloride, dichloromethane, monochloromonofluoromethane, l, 1-difluoropropane and 2,2-difluoropropane, among others.

Since my inventive process depends on absorption or adsorption by thecontaminant of the radioactive labeled material, it is important toinsure that mixing of the radioactive labeled material with thecontaminant be encouraged through use of the proper solvent, throughproviding a long enough time of contact prior to the encouragement ofthe evaporation, and by selecting the proper radioactive labeledmaterial for the type ofcontaminant it is desired to detect.

In addition to the nature and amount of contaminant and the type ofsurface involved there are other facts which the operator of thisinvention will know or control in applying the principles of thisinvention. For example, the temperature and pressure affect the rate ofevaporation and for greatest accuracy it is important that both becontrolled closely. It is possible to carry out a series of referencestudies so that in the event that either temperature or pressure cannotbe controlled positively that reference to graphs or curves be made inorder to correct for such variations. Detection systems such as Geigercounters, scintillation counters, and the like may be so constructedthat temperature and pressure corrections are manually or automaticallytaken into account when the evaporative rate is determined. A furtherfactor affecting the rate of evaporation is the amount, the velocity andtype of gas flowing over the surface being examined. For highestaccuracy the rate of gas will be accurately maintained so thatevaporation from a scrupulously clean surface is always standardized asmuch as possible. Change of the rate ofgas flow can be used to determinemore accurately the amount of contamination under certain conditions andin general high rates of gas flow are used to cause the evaporation ofrelatively high boiling radioactive labeled materials while lower ratesof gas flow are used with lower boiling materials. Proper shielding ofthe surface being cxamined is also important since extraneous gustsofwind or air will sometimes cause false indications of cleanliness.These factors are emphasized not by way of limitations on the broadapplicability of this invention but to stress that proper controls orreferences be used in all measurements. While those skilled in the artwill effect such controls, this emphasis may be a helpful reminder.

Although it is always possible to determine the rate of evaporation froma clean surface just prior to or just after the determination of therate of evaporation from a contaminated surface, it is often ofadvantage to carry out the determination of the rate of evaporation froma scrupulously clean surface in a laboratory under more or less idealsituations and to use such a determination as a reference standard.

The sensitivity of the determination is a function of the amount ofradioactive labeled material added in this inventive process. Thus, thehigher the specific activity of the material, that is the amount ofradioactivity per unit weight, the more sensitive is the test. Thus, ifsufficient radioactivity for convenient detection is present in anamount as low as 1 microgram of material, dilution with 10 micrograms ofcontaminant will cause a very significant reduction in the rate ofevaporation. However, if the same amount of radioactivity is present inmicrograms of radioactive labeled material, the dilution by 10micrograms of contaminant will not greatly affect the rate ofevaporation until a very significant amount of the radioactive labeledmaterial has evaporated.

In general it is desirable to use specific activities in excess of 1.0millicuries per millimole and preferably in excess of 3.0 millicuriesper millimole. For example, l,1,2,2- tetrabromoethane-C at a specificactivity of 3.5 mc/mM has 0.01 microcurie in each microgram of materialand this level is readily detectable. Thus, my inventive method providesa process for the detection of contaminants down to 1 micro gram persquare inch and even lower.

The processes of this invention are useful in many ways. They are usedto detect the presence of hydrocarbon and other contaminants on thesurfaces of many kinds and compositions, as for example, metal plates,valves, tanks and containers, pipes and tubes, and of other metalshapes. The residual hydrocarbon and other contaminants which aredetected by the invention herein described are not in generaldeterminable either qualitatively or quantitatively by prior art. Theuse of the invention herein described is especially impor tant when thesurfaces so examined are used for the storage or transfer of materialswhich react violently with the contaminants so detected since theprocess permits the determination not only of the level of contaminationbut it permits the establishment and determination of realistic levelsof contamination to prevent the possibility of violent reaction.

As can be seen from the above the apparatus used in this inventioncomprises a means for applying a volatile radioactive material to thesurface(s) being examined along with means for effecting evaporation ofthe said material and means for detecting radiation during theevaporation. The applying means places the radioactive material incontact with any contaminant and a gas is used to assist in theevaporation and this gas may be metered over the said surfaces at givenor desired rates. Also, the apparatus includes an aerosol container forthe radioactive material that contains a propellant.

This apparatus is more particularly set out below in the figures anddescription which follows all of which is given for illustrativepurposes only and is not limitative.

In the figures FIG. 1 is a pictorial view of one analysis and controlunit and the probe/dispenser/detector assembly used therewith;

FIG. 2 is a plan view of the said assembly shown in FIG. 1;

FIG. 3 is a front elevation of said assembly;

FIG. 4 is a side elevation of the dispenser in said assembly indispensing position;

FIG. 5 is taken on line 5-5 ofFlG. 4;

FIG. 6 is a side elevation, partially broken, in charge or loadingposition;

FIG. 7 is taken on line 7-7 of FIG. 6;

FIG. 8 is a side elevation ofa detector partially broken away to showthe gas flow means;

FIG. 9 is similar to FIG. 7 showing a different pumping means;

FIG. I0 is a top view of another dispenser;

FIG. 11 is a side elevation of the means shown in FIG.

FIG. 12 is a schematic view of the dispensing means of FIGS. 10 and 11;

FIG. 13 is an electrical block diagram of the analysis and control unit;

FIG. 14 is a block diagram ofthe gas flow system;

FIG. 15 is a block summary;

FIGS. 16 to 16C are illustrative experimental readings obtained with theapparatus of FIG. 1',

FIG. 17 is a side elevation of another dispenser ofthis invention;

FIG. 18 is a pictorial view of an analysis/control unit and probeassembly contained in the same container;

FIG. 19 is an exploded pictorial view showing how the unit and assemblyslide apart;

FIG. 20 is a side elevation showing the microswitch and a dispenser; and

FIG. 21 is an end elevation of the probe assembly.

Referring to FIG. 1 the analysis and control section 10 has a gas supplyand valving system permitting accurate and reproducible control of gasflow to the detector head 11. Also shown are a strip chart recorder 12,four programmed counters 13, a DC ammeter 14 used for expressing countrate, a preset timer 15 which is set to permit substantial evaporationof the solvent used in applying the radioactive test material prior tothe measurement of the evaporative rate of the radioactive materialitself and whose arbitrary value depends on the geometry of the testsurface, temperature, pressure, rate of gas flow, and other factors, apressure gauge 16 which measures gas flow, and a series of lights,switches and controls such as nitrogen adjust valve 17, sequencer on andoff 18, data light 19, nitrogen test switch 20, sequencer signal light21, recorder switch 22 and power switch 23. On the sides are othercontrols, not shown for convenience, such as power inlet, fuses, gasinlet, time base, zero set, gain, scale select, recorder gain and jacketand the tube and power connections to the dispenser assembly.

The probe assembly shown in FIG. I includes a baseplate 24 withadjustable legs 25 insuring stable and level conditions for testing, abubble level detector 26, a target 27 on which the surface to beexamined is positioned, a mechanical arm and bracket assembly 28 forrotating the dispenser and the detec tor to assure proper positioningover the test surface, a precision dispenser 29 which permits dischargeof a metered amount of test solution without substantial change oftitre, a

detector 30 being a Geiger-Mueller tube 32/thin Mylar" protective shieldto reduce background buildup with provision for nitrogen or gas flowbetween the G. M. tube and the surface being tested, and a microswitch31 which turns on the gas flow and sequential operations when thedetector is rotated and positioned over the surface under test.

In the plan view given in FIG. 2 the rotation of the bracket assembly 28is shown by arrows 33. It will be noted that when dispenser 29 isrotated to position it above target 27 to dispense radioactive material,the probe 30 will be in the position shown by dotted lines 34. Likewiseafter dispensing is effected, the dispenser will be moved to position35, the rotation placing probe 30 directly above the center of target27. The probe 30 is mounted on arms 36, shown also in FIG. 3, so that itis pivotable on upright 37 and vertically adjustable by means of setscrew 38. Similarly, the dispenser 29 is mounted on post 39 for verticaladjustment by a setscrew, not shown for convenience, the setscrew 40being provided for rotation of the dispenser head 41. In FIGS. 2 and 3the high voltage line 42 and the gas flow tube 43 are shown in brokenform for clarity ofthe parts beneath.

With further reference to the rotation of dispenser head 41, it will benoted that there are three feeders to the head, these being supplyreservoir 44, charge pump 45 and discharge pump 46. These are shown inFIGS. 2, 4, 5, 6 and 7, for example. In order to fill the supply bottle44, the head 41 is rotated so that the bottle 44 is in the bottommostposition and is vertical. It is then unscrewed from head 41, a suitablethreaded attachment 47 being shown in FIG. 7. This can, of course, besome other type of attachment as for example a threaded cap which fitsover a plain bottle and screws onto the internal threads contained in orheld by the head. In any event, the bottle 44 is removed, is filled withthe radiochemical 48, shown in FIG. 7, placed back into position in thehead 41, and this is then rotated and locked into position by means ofsetscrew 40. This places the reservoir 44 in the position given in FIG.2 or 7.

In FIG. 4 the dispenser is shown in discharge position having beenrotated by the user 49 who turns knob 50. Upon this rotation rocker arm51 contacts discharge pump 46. This pump can also be operated manuallyas shown in FIG. 5. Depression of the plunger 52 forces theradiochemical contained in passageway 53 out through needle discharge 54onto the surface 55 located on target 27. Before describing theevaporation which is then effected, the function of the dispenser willbe further described to explain its loading.

With the bottle 44 in the position shown in FIG. 7 by the user's havingrotated the knob 50 from the position shown in FIG. 4 to the positiongiven in FIG. 6, it can be seen that the passageway 53 is now lined upwith the bottle 44 and charge pump 45. Thus, when the user 49 depressesor activates this pump, air in it and in passageway 53 is forced up intothe bottle. When the pressure is removed, springs 56 force piston 57back up and into the vacuum created flows radiochemical 48. Thus, it canbe seen that containers are provided which are aerosol containers whichcontain a radiochemical, a solvent and a propellant. The system issealed by poly(tetrafluoroethylene) gaskets 58, 58a, and 58b. Thus, theuser having discharged the radiochemical is again ready to alignpassageway 53 with the passageways of discharge pump 46 and needle 54.

With the radiochemical 48 in contact with the test matter on surface 55,the head unit 29 is replaced by probe 30. As this is done, themicroswitch 31 closes and gas begins to flow through tube 43. Thispasses through filter 59 and then tube 60 downwardly and then outthrough an appropriate nozzle or exit 61 so that the gas flows betweenthe bottom of the probe and the surface being examined. This, of course,effects removal by evaporating of radiochemical. Present directly abovethe surface is the GM. tube 32 which, being electrically activated bythe turning of power switch 23, begins detecting the radiation and thechanges therein due to the evaporation, and these changes are convertedinto measures of the rate of evaporation by the analysis unit andparticularly by the count rate 14, recorder 12, if used, and the AA, AB,AC, and AD counters 13.

In FIG. 9 is shown a simplified dispenser having a bellows pumps 46a and45a in place of46 and 45, respectively.

Another embodiment is given in FIGS. l0, l1 and 12 which employs astopcock of a construction different than that used in the embodimentsshown in FIGS. 47. In FIG. 6 the passageway 53 is a polished drilling ina poly(tetrafluoroethylene) cylinder 62 which is mounted by means of pin63 to a brass fitting 64 which is in turn attached to knob 50 to beturned with when it turns. The spring 65 is held in place by member 66,and it bears against cup 67 which in turn urges cylinder 62 so thatpassageway 53 is always ready for alignment. Therefore, simplerarrangement is given in FIGS. 10-12 which also affords the advantage offlushing the metering system.

This embodiment uses stopcock 62a which is tapered, as shown in FIG. 12,to assure alignment and proper seating. It is also connected to knob 50and turns with it. In the position shown the oblique passageway 53a isconnecting the passageway 44a to supply bottle 44 with the passageway45b going to pump 45a, shown in FIGS. 10 and 11. By suitable rotation ofknob 50, passageway 53a will align passageway 69a from solvent supplybottle 69 (FIG. 10) with passageway 68a leading to pump 613. Thus, afterone has delivered radiochemical through needle 54, he can draw cleansolvent which contains no radiochemical from supply 69 and flush out thepassageways.

As shown in FIG. 17, a disposable dispenser is provided comprising asealed container 70 having breakable ends 70a and 70b. While thiscontainer can be made of a variety of materials including metal,plastics or ceramics, glass is preferred. The containers are chargedwith a standard volume We of a radiochemical in a solvent. These arereproducibly made and charged to insure optimum reproducibility intesting. This dispenser can be used instead of dispenser 29, being handheld or held by a clip. In use, the ampule is shaken to get all theliquid into the bottom and then the other end, say 70a, is broken off,and the ampule is turned upside down. End 70b is then broken off and theliquid 70c flows out onto the desired surface. Since the ampule are ofstandard small capillary glass tubing, the inside diameters are fromabout 1 mm. to 2.5 mm., with diameters of less than 2 mm. beingpreferred. In any event, the holdup of liquid is uniform and the amountdispensed is adequately constant.

As discussed above soft beta emitters are preferred and solvents whichboil at least 100 C. below the boiling point ofthe radiochemical areused, it being preferred to have at least a 150 C. differential. Thus,solvents having boiling points below about 75 C. and emitters havingboiling points of at least 200 C. are preferred. The solvent is presentin an amount at least 5,000 times the amount, by weight, of theradiochemical in order to get reproducible volumetric measurements forconstancy of radiochemical dispensing. Of course, much larger ratios,for example, 1 part of emitter in 100,000 parts of solvent, can be used.Of the emitters C-l4, Tritium-3 and Sulfur- 35 are preferred.

It is most important to use very highly purified test solutions. Whilebottles 44 and dispenser 41 are very useful and meet this importantcriterion, the person doing the testing can inadvertently contaminatethe test solution in the filling and dispensing procedures described.Therefore, the dispenser 70 is a very definite advance, for purity isbuiltin and the container, a very inexpensive article, is not usedagain. Thus, dispensers 70, which can be charged with a variety of testsolutions all standardized, afford simple, efficient dispensing.

In FIG. 18 there is shown an embodiment of this invention which ishighly adaptable to the use of dispenser 70. Contained on the front ofportable cabinet 71 are gas flow indicator 16, count rate meter 14, gasadjusting valve 17, data light 19, signal light 21, power switch 23,counter 13, and access door 72, shown open. Within the container 71 andlocated behind door 72 is removable probe assembly comprising the base73 and the G.M. tube unit 74.

As seen in FIG. 19 the base 73 contains a platform 75 having adjustablelegs 76, generally three, the third at rear center being shown in FIG.21, and level bubble 26. Concave section 77 receives and holds thesurfaces 55 which are omitted to show the small drilling 78 that goescompletely through platform 75 permitting the insertion of a small rodfrom the bottom of 75 to push out the test surfaces 55 after the testingis finished. Rails 79 are present to act as guides for the G.M. tubeunit 74 which slides in and out of operative position above platform 75as shown by arrow 75a. Also present is recessed track 80 in which amicroswitch rides as unit 74 is being slid forward to get the G.M. tube32 over a test surface 55 placed in cavity 77. When the G.M. tubereaches that position the spring loaded switch closes the circuit andstarts the analysis sequence.

FIG. 20 shows the G.M. tube assembly 74 in a side elevation position andin position on base 73. The G.M. tube 32 is contained in holder 82 heldon platform 81. Behind the G.M. tube is located gas inlet adapter 83screwed into platform 81 and holding in place gas inlet filter 59a,shown in FIG. 21, which connects via tube 83a to a gas source not shownfor convenience and generally located in container 71. The exit endoffilter 59a connects with a duct 84 in the bottom of platform 81. Thisduct connects in turn with a recess 84a in platform 81 directly beneaththe G.M. tube. Thus, when the G.M. tube 32 is positioned directly abovethe test surface located in cavity 77, the gas goes through ducts 84 and84a and sweeps the test surface in cavity 77. The microswitch 85 is heldin place by cover plate 85a and is actuated by element 85b, generally aretractable wheel, which rides in track 80. Upon reaching the testposition, this element 85b has been pushed sufficiently to close thedesired circuit.

The container 82 also serves as a holding means for dispenser 70. Clip100 is pivotably mounted on element 101 held by bracket 102 to container82. As shown in FIG. 20, the dispenser, after it has been well shaken toget all the liquid into the bottom end, is placed in clip 100. The topend 70a is then broken off and with dispenser 70 directly above thesurface to be tested which has been placed in holder 77, the tube isupended, and with the sealed bottom end now at the top it is broken offand the liquid is allowed to run onto the surface. Unit 74 is thenpushed into the final position that activates microswitch 85, and theanalysis is begun and made.

An electrical circuit is shown in FIG. 13. The power source 86 isgenerally the conventional 60 cycle AC I 15 volt source and is fed totransformer 87 whose secondaries provide high voltage AC and three lowvoltage sources. Through use of a standard diode bridge and filtercircuit 88 the AC current provided by the transformer is converted to460 volt DC current which is fed to the G.M. tube 32. The three standardlow voltage converters 89a, 89b 89c provide 12 volt DC current, andthese currents are used to operate the basic electronic circuitry whichcomprises amplifier 90, monostable circuit 91, amplifier and data lightcircuit 92, electronic counter and amplifier 93 and rate meter circuit94. The output of the G.M. tube 32 is fed to amplifier 90 and theamplifier spikes are fed to unit 91 where they are converted to squarewave signals. These are then fed in part to the rate meter circuit 94which activates meter 14 and recorder I2, if used. The other portion ofthe square waves supplied by 91 are fed to the amplifier and data light92 which activates data light 19 and counter/amplifier 92. A function ofthe counter is supplied through the cyclic timer 95 to theelectromechanical counters 13. The circuitry shown in FIG. 13 may beused for both embodiments shown in FIGS. 1 and 18.

FIG. 14 is a block diagram of the gas or nitrogen supply system. Asource 96 feeds the gas through a solenoid valve 97, present in theembodiment of FIG. 1, but not in that of FIG. 18. This valve is actuatedby microswitch 31 or test button 20 shown in FIG. 1. The gas in then fedthrough an adjustable needle valve 17 and through a calibrated orifice98 whose pressure drop is measured by meter 16 and from there throughfilter 59 (or 59a) to the annular space between test surface 55 and thebottom ofG.M. tube 32.

In summary, H6. 15 shows power source 86 and gas source 96 being fedinto analysis and control unit (or 71). The high voltage supply 42 tothe GM. tube or probe assembly 11 or 11a with gas supply 43 andconnectors 99 for synchronizing microswitch 31 (or 85).

The various parts are readily available or assembled from commerciallyavailable parts or units. For example, recorders (12) are available fromRustrak Instruments Co., Inc, Manchester, N.H., Model 88 beingapplicable. Constant rate meters (16), such as Model l93lFS-l00 Ma canbe obtained from Weston Instruments, Inc, of Archibald, Pa. The AmperexElectronics Corp. of Hicksville, L.l., N.Y. supplies G.M. tubes (32) as,for example, its Model 18526 which is readily modified as describedpreviously. A cyclic timer (95) which may be used is obtainable from theCramer Division of Giannini Controls Corp. at Old Saybrook, Conn. Alsoof that address is the Bristol Division of The Vocaline Co. of Americawhich supplies timers (15), for example, Model 6210-305 -Bl. Filters (59or 59a) can be obtained from the Millipore Filter Corp. of Bedford,Mass., and suitable gas flow gauges are available from F.W. Dwyer Mfg.Co. of Michigan City, Ind. as, for example, its Model 200 l. The use oftransformers, diodes, resistors, capacitors, transistors and the likeis, of course, well known. Further, it is to be appreciated that certainelements may be eliminated, provided that the apparatus affords thecontrol of evaporation of gas flow coupled with the accurate counting ormeasuring of radioactivity afforded by this invention.

In FlGS. 1616C are shown typical numerical values on counters 13. FIG.16 shows background-that is, numbers normally obtained on surfaces priorto the addition of test solution. Those in FIG. 16A are for a relativelyclean surface upon testing. If such a surface is contaminated by a merefingerprint smudge, the numbers obtained are substantial as shown in H6.168. If a successful attempt is made to remove the fingerprint, thenvalues like those in FIG. 16A are again obtained but if the removal isnot successful, as by wiping with a dry cloth, then intermediate valueslike those in FIG. 16C may be obtained. These simple experimentsdemonstrate efficacy of the apparatus and methods of this invention.Also, these values represent a function of sequential areas under theevaporation curve which is obtained by recording the count rate on astrip chart recorder; the curve thus obtained is the evaporation curve.

While the invention has been disclosed herein in connection with certainembodiments and certain structural and procedural details, it is clearthat changes, modifications or equivalents can be used by those skilledin the art; accordingly, such changes within the principles ofthisinvention are intended to be included within the scope of the claimsbelow.

lclaim:

1. Apparatus for dispensing a metered amount of a liquid which apparatuscomprises a device which contains a rotatable head which contains (a) atleast one removable reservoir for said liquid which reservoir can beplaced in an upright position and in an up-ended position as desired andin conduit relationship with an outlet for said liquid from saidreservoir and said head; ([2) an outlet in said head in said conduitrelationship; (c) means for creating a pressure on said liquid in saidreservoir; means for forcing said liquid out of said reservoir and outof said outlet; and means for rotating said head.

2. Apparatus in accordance with claim 1 which includes a means forplacing and supporting said outlet to afford placing liquid to bedischarged where desired.

3. Apparatus in accordance with claim 2 in which said placing andsupporting means comprises a support on which said means is pivotablymounted to swing said outlet into and out of operative position asdesired.

4. Apparatus in accordance with claim 2 In which said placing andsupporting means has pivotably connected to it a de' tection device fordetecting the presence of said liquid forced out of said outlet whichdetection device can be swung into and out of operative position asdesired.

5. Apparatus in accordance with claim 1 in which said outlet for saidliquid from said head comprises a needle.

6. Apparatus in accordance with claim 1 which includes a rotatable armwhich activates and deactivates, as desired, said means for forcing saidliquid out of said reservoir.

7. Apparatus in accordance with claim 1 in which said means for forcingsaid liquid out of said reservoir includes a pump that creates a vacuumin a conduit within said device and said pressure above the liquid insaid reservoir.

8. Apparatus in accordance with claim 1 in which said means for forcingsaid liquid out of said head is a discharge pump that applies airpressure on any liquid contained in said outlet.

9. Apparatus in accordance with claim 1 in combination with a means fordetecting the presence of said liquid forced out ofsaid outlet.

1. Apparatus for dispensing a metered amount of a liquid which apparatuscomprises a device which contains a rotatable head which contains (a) atleast one removable reservoir for said liquid which reservoir can beplaced in an upright position and in an up-ended position as desired andin conduit relationship with an outlet for said liquid from saidreservoir and said head; (b) an outlet in said head in said conduitrelationship; (c) means for creating a pressure on said liquid in saidreservoir; means for forcing said liquid out of said reservoir and outof said outlet; and means for rotating said head.
 2. Apparatus inaccordance with claim 1 which includes a means for placing andsupporting said outlet to afford placing liquid to be discharged wheredesired.
 3. Apparatus in accordance with claim 2 in which said placingand supporting means comprises a support on which said means ispivotably mounted to swing said outlet into and out of operativeposition as desired.
 4. Apparatus in accordance with claim 2 in whichsaid placing and supporting means has pivotably connected to it adetection device for detecting the presence of said liquid forced out ofsaid outlet which detection device can be swung into and out ofoperative position as desired.
 5. Apparatus in accordance with claim 1in which said outlet for said liquid from said head comprises a needle.6. Apparatus in accordance with claim 1 which includes a rotatable armwhich activates and deactivates, as desired, said means for forcing saidliquid out of said reservoir.
 7. Apparatus in accordance with claim 1 inwhich said means for forcing said liquid out of said reservoir includesa pump that creates a vacuum in a conduit within said device and saidpressure above the liquid in said reservoir.
 8. Apparatus in accordancewith claim 1 in which said means for forcing said liquid out of saidhead is a discharge pump that applies air pressure on any liquidcontained in said outlet.
 9. Apparatus in accordance with claim 1 incombination with a means for detecting the presence of said liquidforced out of said outlet.